Stability of L-(+)-ascorbic acid in alginate edible films loaded with citric acid for antioxidant food preservation

• Citric acid (CA) and ascorbic acid (AA) loaded alginate films were developed.
• Higher storage relative humidity and glycerol levels rose the AA hydrolysis in films.
• CA did not vary but modified the kinetic order of film browning subsequent to AA loss.
• AA and CA were 100% recovered after film casting.
• The lowest glycerol content was related to longer antioxidant half-life of films.

Alginate of known copolymer composition was applied to antioxidant film developed by loading L-(+)-ascorbic (AA) and citric (CA) acids. Relative humidity (RH, 33.3–75.2%) of storage (25.0 °C) and glycerol (plasticizer) level, separately and through their interaction, decreased the AA hydrolytic stability and, hence, the antioxidant half-life of films. Glycerol can facilitate the water penetration from the environment into the polymeric network. The CA content did not vary during film storage. Film browning was then associated to AA degradation. However, CA slowed down the browning development at longer storage times because of the changes in the kinetic order. It may catalyze the formation of unstable color compounds. The present work permitted to determine that AA and CA were 100% recovered after film casting. Also, it allowed finding the adequate film composition and period where the alginate film supporting AA and CA can be used as an antioxidant active interface for food preservation.